This study reports on the potential of comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GC×GC−ToF MS) for the exhaustive untargeted characterization of the volatile and semi-volatile analytes migrating from four commercial polypropylene food containers into four simulants (water, 3% acetic acid, 10% ethanol, and isooctane) according to European Regulation 10/2011. Collected extracts were concentrated and directly subjected to GC×GC−ToF MS analysis without any further treatment to preserve migrants integrity. As expected, the nature and total number of compounds detected in the migrates depended on both the brand (i.e., manufacture and/or sterilization procedure) and the simulant applied. In total, 107 analytes, including some less volatile compounds, were either positively or tentatively identified in the investigated simulants, a number of these compounds being reported for the first time as migrants from this type of material. A database containing chromatographic, mass spectral and partition information concerning these compounds, plus 23 remaining unidentified, is provided.

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The use of room temperature ionic liquids (ILs) as green solvents is an emerging and innovative technology, which is quickly expanding in carbohydrate chemistry. However, information about solubility of low molecular weight carbohydrates (LMWC) in ILs is still scarce. This study provides new solubility data for several LMWC dissolved in methylimidazolium-based ILs. Different solubility values have been obtained for carbohydrates depending on their structure. In general, ketoses are more soluble than their corresponding aldoses, and trisaccharides are more soluble than mono-and disaccharides, although some exceptions have been observed depending on the tested IL. [BMIM][MeSO 4 ] and [HMIM][Cl]acted both as solvent and as catalyst for dehydration of ketoses (fructose and tagatose) into 5-hydroxymethylfurfural at 318 K. These findings pointed out the potential of ILs as an interesting alternative solvent for new applications in applied carbohydrate chemistry.

IntroductionAs indicated in previous chapters, bioactive carbohydrates, both naturally occurring and synthesized, consist of mixtures with different degrees of polymerization (DP), glycosidic linkages or monosaccharide unit composition. Moreover, those present in natural products can be part of complex samples constituted by other compounds including lipids, proteins, and so forth .Fractionation and purification procedures are required for both oligosaccharide production and analysis. Regarding the production of bioactive oligosaccharides, the removal of mono-and disaccharides fractions could be required to evaluate their functional properties (e.g. in vitro prebiotic activity), to obtain enriched bioactive fractions or to use them as food ingredients in specialized products for individuals with different disorders (diabetes, lactose intolerance, etc.), as well as in low calorie foods with a reduction of some mono-and disaccharides.Fractionation of oligosaccharides based on their glycosidic linkages or monosaccharide composition can also be crucial for the elucidation of carbohydrate structures, and consequently, to gain insight into the structure/function relationship. Although analytical techniques have noticeably advanced over the past few years, chromatographic, spectrometric or spectroscopic tools are still not sufficient to achieve an exhaustive characterization of oligosaccharides present in complex mixtures.The most commonly used purification steps are centrifugation, precipitation, and / or filtration. These wide-ranging procedures are commented in each corresponding chapter and they will not be discussed here since this chapter will focus on effective tools to fractionate specific bioactive oligosaccharides from complex carbohydrate mixtures. Nevertheless, some exceptions will be made, as could be the case of the continuous enzymatic production of galactooligosaccharides (GOS) and their separation from the recycled enzyme or the fractionation of xylooligosaccharides (XOS) from biomass, both accomplished by membrane filtration processes (section 15.2).Fractionation of oligosaccharides is not a straightforward task due to the structural complexity, which also includes similarities in carbohydrate structures. The search for fractionation techniques that obtain high selectivity and efficiency, using small solvent volumes, environmentally friendly and inexpensive, is one of the main aims of both researchers and industries. Figure 15.1 Scheme of the techniques used for the fractionation of food oligosaccharides.This chapter deals with the different procedures used for the fractionation of bioactive carbohydrates for either producing functional ingredients or preparing samples for further analysis. As summarized in Figure 15.1, this chapter will cover not only advances in traditional methods but also novel techniques with potential for use in this field. Membrane techniquesMembrane separation processes are normally driven by a pressure gradient in which the membrane fractionates components of a liquid mixture ...

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